Energy saving is of prime importance for wireless devices, especially those wireless devices that operate on either harvested energy or very small batteries such as coin cells. With the explosion of portable and wearable devices along with the miniaturization of electronics, computing capability is finding itself in many applications for which one would not have expected computerization in the recent past. Because, however, many of these devices have low processing demands and it is greatly desirable to extend battery life, many approaches have been taken to reduce power consumption to enhance battery life.
Approaches to reduce energy consumption include continuously trying to reduce circuit size and unnecessary functionality to reduce required power. Additionally, high gain antennas with low-power transmissions and advanced error correction techniques have been utilized to reduce power. One common approach to saving power is to place systems, circuit blocks, and even circuit elements into a powered down or sleep state until needed. Because many of these portable electronics utilize a communication protocol with a periodic beacon, such as the connection events in Bluetooth, designers have implemented designs to place radio transceiver circuitry into a sleep mode in between beacons. With such designs, a receiver circuit is powered back up prior to an expected beacon transmission time (or other communication event) by a wake up timer in the remote device. Because of limited precision and drift in these low power wake up timers, these receiver circuits are often powered backup unnecessarily early for the sake of ensuring that the transmitted beacon is not missed. These unnecessary early wake ups waste energy. A need exists, therefore, to improve the precision of the wake up timer to reduce this waste.
The use of the same reference symbols in different drawings indicates similar or identical items. Unless otherwise noted, the word “coupled” and its associated verb forms include both direct connection and indirect electrical connection by means known in the art, and unless otherwise noted any description of direct connection implies alternate embodiments using suitable forms of indirect electrical connection as well.